A comparative investigation has been made of the microstructure and magnetization reversal behavior of nanocomposite SmCo_(5)/Sm_(2)Co_(17) powders prepared by intensive milling and subsequent annealing. It was found that the saturation magnetization increases monotonically with the increase of the volume fraction of Sm_(2)Co_(17) at the expense of the coercivity. However, the remanence and the energy product first increase and then decrease with further increase of the fraction of Sm_(2)Co_(17). The highest remanence of 0.72 T and energy product of 78 kJ/m~(3) are obtained in the powders with 80 and 60 Sm_(2)Co_(17), respectively. All the hysteresis loops exhibit a magnetically single-phase behavior. X-ray diffraction results reveal that the coexistence of two phases is found in the mixture of SmCo_(5)/Sm_(2)Co_(17) powders. The demagnetization processes of the SmCo_(5)/Sm_(2)Co_(17) powders are similar to those of nanocomposites consisting of hard and soft phases, in which the exchange-spring magnet behavior was observed. Positive as well as negative deviations in Wohlfarth's remanence analysis (δM-plot) have been observed, indicating complex magnetic interactions in these materials.
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